Hydraulic apparatus with axially aligned hydraulic units

ABSTRACT

Two hydraulic units, each operable as a pump or hydraulic motor, have coaxial shafts in end-to-end relationship which can be coupled and disengaged from each other by a coupling. Valve means hydraulically connect the two units, so that a single unit can be operated as a pump or motor, that both units can be simultaneously operated as pumps or motors, and so that the two units can form a hydrostatic transmission in which one unit operates as a pump driven by a prime mover, and the other unit operates as a hydraulic motor.

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Widmaier aieiit [15 1 mamas lFeh.22, 1972 [54] IHIYlDAIUILll C APPARATUS WITH AXllAlLILY ALllGNlED HYDRAIUILHC UNHTS [72] Inventor: Dieter Widmaier, Fellbach, Germany [73] Assignee: Robert Bosch Gmhllil, Stuttgart, Germany [22] Filed: June 3, 11970 21 Appl. No.: 44,329

[30] Foreign Application Priority Data July 23, 1969 Germany ..P 19 37 347.8

[52] US. Cl. ..60/53 A, 417/429, 91/474 [51] ]lnt.Cl ..1F1l6d 311/02 [58] Field of Search ..60/53 A, 52 US, 6; 91/472,

[56] References Cited UNITED STATES PATENTS 7/1951 Nixon ..60/53AX 4/1960 Lupin ..4l7/319 Primary Examiner-Edgar W. Geoghegan Attorney-Michael S. Striker [57] ABSTRACT Two hydraulic units, each operable as a pump or hydraulic motor, have coaxial shafts in end-to'end relationship which can be coupled and disengaged from each other by a coupling. Valve means hydraulically connect the two units, so that a single unit can be operated as a pump or motor, that both units can be simultaneously operated as pumps or motors, and so that the two units can form a hydrostatic transmission in which one unit operates as a pump drivenby a prime mover, and the other unit operates as a hydraulic motor.

14 Claims, 8 Drawing Figures PATENTEDFEB 22 m2 3, 643 ,434

SHEET 1 or 5 INF EN TOR. Dieier WIDIIAIER M-l/{QM Quin,

PATENTEUFB22 1972 3, 43 ,43

SHEET 2 OF 5 INVENTOR. Diefer WIDMAIER PATENTEUreazzMz 3,643,434

SHEET 5 OF 5 Fig-8 INVENTOR.

' Diefer WID/MIER' IIYDIIAUIJIC APPARATUS WITH AXIAILIL! ALIGNIED HYDRAULIC UNITS BACKGROUND OF THE INVENTION The present invention relates to a hydraulic apparatus composed of two hydraulic units having coaxial rotors, and at least one shaft which can be driven by a prime mover. Hydraulic apparatus of this type is disclosed in the US. Pat. No. 2,910,008 and US. Pat. No. 3,183,845. The apparatus of the prior art can be used as a double pump or double motor, and can be adjusted to discharge an amount of fluid between zero to the maximum volume which can be pumped by both hydraulic units. The apparatus of the prior art has the disadvantage that always both hydraulic units have to be driven, even if a small output volume of fluid is required. As a result, leakage losses, friction losses, wear and other liquid losses are great, and the units are not used efficiently. Furthermore, the hydraulic apparatus of the prior art can serve either as a variable pump, or as a variable motor, but cannot be used as a hydraulic transmission.

CROSS-REFERENCE TO RELATED APPLICATION My copending application Hydraulic Apparatus with Interconnected Units," filed on May 7, 1970, Ser. No. 35,427, is directed to related subject matter.

SUMMARY OF THE INVENTION It is one object of the invention to overcome the disadvantages of known hydraulic apparatus including two hydraulic units, and to provide an apparatus which, under specific operational conditions, has very low losses, and which can be adapted to different load requirements.

Another object of the invention is to provide a hydraulic apparatus which can be used for different purposes, and economically operated.

With these objects in view, the present invention provides a hydraulic apparatus including two hydraulic units having two coaxial shafts. A coupling means is provided for selectively connecting or disconnecting the shafts. This has the advantage that, if only a small amount of pressure fluid is required, one of the two hydraulic units operates as a pump, while the other is inoperative. In this manner, leakage losses, friction losses, wear and liquid losses can be proportionately low, so that the output of the prime mover is reduced. The same advantage results when only one hydraulic unit is driven as a motor whose output is sufficient to overcome the load.

It is particularly advantageous, when the fluid pumped by one of the hydraulic units, is applied through a valve to the other hydraulic unit while the shafts of the two units are disconnected by a disengaged coupling. In this case, a hydro static transmission is formed by the two hydraulic units, and the hydraulic unit operating as a hydraulic motor can be used for driving other apparatus, for example a vehicle. The hydraulic apparatus of the invention can be used as a single pump or a single motor, as a double pump or double motor, or as a hydrostatic transmission, so that it has a universal use. The apparatus can be used as a hydrostatic transmission drive for a vehicle, which is then stopped at a work place, where the hydraulic apparatus is used as a single pump or double pump.

One embodiment of the invention comprises first and second hydraulic units having first and second stator means and first and second rotary means, respectively, the first and second rotary means having a common axis; connecting means, such as coupling means for the shafts of the two units, having an engaged condition connecting the first and second rotary means so that the first and second hydraulic units are simultaneously operated as pumps when the first rotary means is driven, and as hydraulic motors when a fluid medium under pressure is supplied to the first hydraulic unit, and a disengaged condition connecting the first and second rotary means so that only the first hydraulic unit operates as a pump or mo tor. respectively; and operating means for placing the con necting means selectively in the engaged and disengaged positions. A housing envelopes the first and second hydraulic units and the connecting means, and has a sealed opening through which a lever of the operating means projects to the outside.

In the preferred embodiment of the invention, valve means and conduit means hydraulically connect the first and second hydraulic units. The valve means are operable between a first control position in which, in the disengaged condition of the connecting means, only the first hydraulic unit operates as a pump or motor, a second control position in which in the engaged condition of the connecting means, the hydraulic units operate both as pumps, or motors, and a third control position hydraulically connecting the first and second units so that in the disengaged condition of the connecting means, the second hydraulic unit operates as a hydraulic motor hydraulically driven by the first unit operating as a pump and forming a hydrostatic transmission with the same.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is an axial sectional view illustrating a first embodiment of the invention;

FIG. 2 is a fragmentary view illustrating a modified detail of the apparatus shown in FIG. ll;

FIG. 3 is an axial sectional view illustrating a second embodiment of the invention;

FIG. 4- is a cross-sectional view taken on line l-l in FIG. 3;

FIG. Sis a sectional view taken on line V-V in FIG. 4-;

FIG. 6 is a fragmentary side view taken in the direction of the arrow VI in FIG. 4;

FIG. 7 is partly a schematic side view and partly a diagram matic view illustrating apparatus according to the invention in combination with a control valve means; and

FIG. 8 is partly a schematic side view, and partly a diagrammatic view illustrating apparatus of the invention which has a reversible output shaft, and is provided with control valve means for placing the apparatus in different operational cow ditions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. l, a housing I is closed by a cover 2. Within the housing, two hydraulic units in the form of axial piston engines 3 and 4 are arranged in end to-end relation. The hydraulic unit 3 has a cylinder body 5 with several parallel bores 6 in which pistons 7 are mounted for sliding movement. The ends of the piston abut a slanted swash plate 9 which is mounted for tilting movement on a pivot 8 on shaft I2. The angle of swash plate 9 can be adjusted by a servomotor 110 which is connected by a linkage with the swash plate 9. The cylinder body 5 has an end face in contact with a smooth surface on a control valve plate II which is fixedly secured to housing I. Cylinder body 5 is rotated by shaft 12 with which it is connected by a toothed annular portion of shaft I2 which engages corresponding recesses in the cylinder body 5. A prime mover motor, not shown, is used for driving shaft 12.

The second hydraulic unit A is also an axial piston engine which has a rotary cylinder body I4 with bores IS in which pistons 116 are mounted for sliding movement in sealed condition. The piston abuts another swash plate 17 which is not tiltable in the embodiment of FIG. I, but extends at a predetermined angle to the axis of shaft 18 which is connected by teeth 211 with corresponding recesses of the cylinder body It Cylinder body 5 with shaft I2 constitutes a first rotary means of the first unit, and cylinder body M with shaft III coir stitutes a second rotary means of the second hydraulic unit.

Shafts l2 and 18 have adjacent end portions arranged in end-to-end relationship, and a coupling or connecting means 19 is provided for connecting or disconnecting the end portions of shafts 12 and 18. On the end of shaft 12, an outer annular set of axially extending projections and recesses 20 is provided which cooperates with a corresponding annular set of axially extending projections and recesses 21 on shaft 18. The projections and recesses 21 are spaced a predetermined distance from the end of shaft 18. The coupling means 19 has two sets of inner axially extending projections and recesses 22, 23, of which the projections and recesses 22 are always connected with the projections and recesses 20, while the projections and recesses 21 by shifting the coupling means 19, which has the form of a coupling sleeve. A bushing 24 is arranged between the sets of projections and recesses 22, 23 and at the inner annular surface of coupling sleeve 19, in which the smooth portion 25 of shaft 18 is rotatably mounted. Consequently, coupling sleeve 19 also serves as an aligning bearing for the end portions of shafts 12 and 18. Shaft 12 is also mounted in a ball bearing 25 supported in the cover 2, while shaft 18 is mounted in a ball bearing 26 in the other part of housing 1. The outer set of projections and recesses 21 on shaft 18 also serves for connecting shaft 18 with the cylinder body 14, in addition to the coupling function disclosed above.

At the outer peripheral surface of coupling sleeve 19, a ring 27 is provided from which connecting rods 28 pass through bores 29 in cylinder body 14 to an operating member 30 mounted on shaft 18. The operating member 311 is axially movable on shaft 18, but is connected with the same for rotation. Operating member 30 is located outside of the rotary parts of the hydraulic unit 4. A flange 31 on operating member 30 is embraced by a portion of an operating lever 32 which can be tilted by a rod 33 by a manual operation. The opening through which lever 32 passes, is sealed by sealing means 34 so that no pressure fluid can escape from housing 1, 2.

In the control valve plate 11, arcuate, part-circular recesses 35, 36 and 37, 38 are provided for the two hydraulic units 3 and 4. The recesses 35 and 37 are connected with each other and to a bore 39 which communicates with a connector on the housing, similar to the threaded bore 45, to which a conduit can be threaded for obtaining a connection between outlet bore 39 and a container for a pressure fluid, not shown.

The recesses 36 and 38 are also connected with each other by a space 40 in which a check valve 41 is disposed which opens in the direction from recess 38 toward recess 36. Check valve 41 is a hollow body 42 with a conical portion for engaging a corresponding seat, and has several openings 43. From the upper part of the space 40, which is adjacent the recess 36, a duct 44 extends to a threaded bore 45 which penetrates the housing 1, and can be used for threading in a connector line to a consumer apparatus. The bore 39 at the recesses 35 and 37 is connected in the same way, but without the use of a check valve, with a container.

When the apparatus is used as a single pump or as a double pump, shaft 12 is driven by a prime mover motor, not shown. When the coupling sleeve 19 is in the illustrated position, the hydraulic unit 4 is disconnected from shaft 12 and thereby from the prime mover, and is at a standstill, while the hydraulic unit 3 is driven and operates as a single pump. In the usual manner, pistons 7 suck fluid through the recess 35 and bore 39 from the container, not shown, and the fluid is pumped into the recess 36 from where it flows through outlet 45 and to the consumer. Since the swash plate 17 is not adjustable in the embodiment of FIG. 1 and always remains in the illustrated slanted position, the hydraulic unit 4 could rotate if there were a connection between the recesses 36 and 38. This is prevented by the check valve 41 which, as illustrated in FIG. 1, abuts its seat and closes the connection between recess 36 and recess 38. During operation of the hydraulic unit 3 as a single motor, pressure fluid is pressed into the bore 45 which flows through the cylinder body 5, operates the pistons 7, and finally flows out of bore 39. It will be noted that there is always high pressure at the recesses 36 and 38, and low pressure at the recesses 35 and 37, irrespective of whether hydraulic unit 3 operates as a single motor or a single pump.

If the hydraulic apparatus of FIG. 1 is to operate as a double pump, operating lever 32 is used for displacing operating member 30 away from cylinder body 14 so that coupling sleeve 19 is pulled by linking rods 28 to a position in which the inner annular set of projections 23 is connected with the outer annular set of projections 21 on shaft 18. Coupling sleeve 19 is only shifted so far that the inner annular set of projections and recesses 22 remains in mesh with the outer annular set of projections and recesses 20. Since the shafts of the two units are coupled with each other, they rotate in synchronism, and when shaft 12 is driven by the prime mover, not shown, both hydraulic units 3 and 4 operate as pumps and pump the maximum amount of fluid. The check valve 41 is lifted by the pressure fluid supplied by hydraulic unit 4 to recess 38, the the pressure fluid can flow through bore 43 into outlet bore 45.

When the servomotor 10 is used, the displaced volume of the hydraulic unit 3 can be varied in the range between zero and a maximum. The output of the hydraulic unit 4 is constant, since swashplate 17 has a permanent angle. After hydraulic unit 3 has been regulated between zero and maximum output, the second hydraulic unit 4 can be connected by operation of the coupling means 19, and when the first hydraulic unit 3 is again regulated from zero to a maximum, the output is gradually increased so that the hydraulic apparatus is capable of being regulated between zero output and the maximum output of both pumps, although only one hydraulic unit 3 is regulatable.

In the modification illustrated in FIG. 2, the bearing bushing 24 is replaced by a needle bearing which is arranged in a widened end portion 51 of shaft 51 of the first hydraulic unit. The widened end portion 51 has an annular outer set of projections and recesses 52, which can be engaged by the inner annular set of projections and recesses 53 of a coupling means 54 which is operated as described with reference to FIG. I.

The valve plate means 55 is also modified, and the part-circular recesses 56, 57, 58, 59 are not connected with each other, but each recess 56 to 59 has its own duct 60, 61, 62, 63, respectively. Each duct 60, 63 is connected with inlet bores, not shown, for a pressure fluid, and each duct 61, 62 is connected with an outlet, not shown.

Consequently, it is not necessary to provide a check valve between the recesses 57 and 58, as will be explained further with reference to FIGS. 7 and 8. The embodiments of FIGS. 1 and 2 have the advantage that the coupling sleeve of couplings 19 and 94 form an additional bearing for both shafts so that the same remain axially aligned during rotation. This is advantageous for small hydraulic units in which the shafts are comparatively short, but if very large hydraulic units with long shafts are used, it is preferred to provide two bearings for each shaft, as shown for the embodiment of FIG. 3. The two hydraulic units are constructed as explained before, and corresponding parts are provided with like reference numerals. Each hydraulic unit has its own control valve plate. The control valve plate 65 cooperates with the hydraulic unit 3, and the control valve plate 66 cooperates with the hydraulic unit 4. The control valve plate 65 supports a roller bearing 67 in which shaft 68 is mounted in addition to the bearing at the end of shaft 68. The control valve plate 66 has a roller bearing 69 which is the second bearing for the shaft 70. The end portion of shaft 70 adjacent the end portion of shaft 68 has an annular outer set of projections and recesses 71, while the end portion of shaft 70 has an outer annular set of projections and recesses 72. The length of the set of projections and recesses 71 is at least twice the length of the set of projections and recesses 72.

On the outer set of projections and recesses 71, a coupling sleeve 77 is mounted by means of an inner annular set of projections and recesses 74. Coupling sleeve 74 is again operated by means of an operating lever 75 which is mounted for angular movement on an intermediate member 76 against which the two valve plates 65 and 66 abut.

Operating lever 75 engages a nonrotatable flange 77 which is mounted for relative rotation on coupling sleeve 73 by means of a ball bearing. Lever 75 passes through housing ll through a sealed opening "73 so that no pressure fluid can escape from the interior of the housing.

Control valve plate as has passages '79 which communicate with part-circular recesses 99, ill in the intermediate part 76, as also shown in FIG. 4,. Control valve plate as has passages which communicate with part-circular recesses 93, M in the intermediate part 76.

The recess 99 is connected by a channel 95 passing through the intermediate part 76 and the housing wall I, and ending on a flange surface 96 of the housing l. A corresponding channel 97 is connected with the recess 93, and corresponding channels 99 and 99 connect the recesses 99 94 with the flange surface 96, as best seen in FIGS. l 3 and s Control valve means I99, (and lid) which will be described with reference to FIGS. 7 and 9, are mounted on the surface of the flange an.

Shaft 79 has at the end projecting out of the housing, an annular set of projections and recesses 99. An output shaft 9ll is coaxial with shaft 79, and has an outer annular set of projections and recesses 92. Shafts 99 and 9i can be connected by operation of a coupling 93 which is slidingly mounted on the output shaft 9i, and which mounts a nonrotating flange 94- connected with a lever 95. The coupling sleeve 93 has an inner annular set of projections and recesses 96 which match the outer sets of projections and recesses 99, 92. The hydraulic apparatus illustrated in FIGS. 3 to s, operates substantially as described with reference to the apparatus of lFlG. l, and further details will be explained with reference to FIGS. '7 and 8. The hydraulic apparatus shown in FIG. 7' substantially cor responds to the apparatus described with reference to FlG. ll, and may or may not be provided with check valve ill.

A control valve 199 is connected with the outlet of the two hydraulic units 3 and 4-, and has two control positions. In the position I, the discharged fluid can flow through conduit I97 and valve I99 to a consumer, and in the position II of control valve 199, no fluid can be discharged from the apparatus.

The passage 39 is connected with the conduit till which connects with a second control valve T92 and ends in a container 193. The container is associated with an auxiliary pump I94 which sucks fluid from the container, and pumps the same through a line M5 to control valve 1192 by which the fluid is returned through conduit I9 6 into the container 1 93 if the control valve I92 is in position II. The hydraulic units 3 and ti are directly connected by passages I99 and W9 in the control valve plate lll.

When the coupling sleeve l9 is moved to a position in which shafts l2 and l9 are not coupled, and when the coupling sleeve 93 of shaft 19 and output shaft 91 in the embodiment of FIG. 3, is also disengaged, only the hydraulic unit 3 operates as a single pump when shaft 12 is driven by prime mover, not shown. The control valves I99 and i912 are both in the control positions I. The hydraulic unit 3, operating as a pump, sucks from conduit WI and through control valve I922, fluid from the container 193 and transports the same through control valve I99 and conduit 19'? to a consumer. Since it is assumed that the check valve ll is omitted in FIG. '7, it must be assumed that swashplate I7 is mounted on shaft T9 for angular tilting movement, and when only hydraulic unit 3 operates as a pump, swashplate 17 is placed in a position located in the plane perpendicular to the axis of shaft 119 so that the hydraulic unit t cannot rotate. When pressure fluid is admitted through conduit 197, and low pressure fluid is discharged through conduit ll9l into the container 193, the hydraulic unit 3 operates as a hydraulic motor.

When coupling i9 is engaged to connect shafts i2 and T9, and the coupling 93 is disengaged, the hydraulic units 3 and l both operate as a pump when the swashplate it! is placed in a selected angular position The two hydraulic units 3 and i discharge pressure fluid through conduit W9 and control valve 199 to the consumer conduit 197. When the apparatus is to be operated as a double motor, pressure fluid is admitted through conduit T97 and control valve 199.

It is a particular advantage of the present invention that the hydraulic apparatus can also be used as a hydrostatic transmission in which the hydraulic unit 3 operates as a pump, and the hydraulic unit operates as a hydraulic motor. For this purpose, coupling 19 is disengaged so that shafts l2 and B9 of the rotary means of the two hydraulic units 3 and 4 are disconnected. Coupling 93 is engaged so that shaft 119 of hydraulic unit t is coupled with the output shaft 91. The two control valves 1199 and 19?; are placed in the control position II.

The hydraulic unit 3, and more particularly shaft 112, is driven by a prime mover, not shown, the pressure fluid pumped by hydraulic unit 3 flows directly through passage 1199 into the hydraulic unit l, since control valve I99 in the position ll closes the outlet 45 to the consumer conduit 197. The fluid pumped into the hydraulic unit t causes rotation of the same so that hydraulic unit t operates as hydraulic motor and drives the output shaft 9i through the coupling 93. The hydrostatic transmission 3, d, 199, I92 operates in a closed circuit, and the fluid displaced by the hydraulic unit 3 and discharged into the hydraulic unit t flows directly from the hydraulic unit t back into the hydraulic unit 3 through passage 199. The connection of conduit 1911 to container 1193 is closed by control valve 192 in the second control position ll.

When a hydrostatic transmission is operated in a closed cir cuit, leakage losses occur which have to be compensated. This is effected by the auxiliary pump I94 which in the control position I of valve 192, pumps through conduits i951 and Hill fluid into the passage 39 which is connected with the output of the hydraulic unit and the input of the hydraulic unit 3, The auxiliary pump 19 i operates at low pressure and compensates the leakage losses.

Shaft 911, which is driven by the hydraulic transmission 3, i, may be connected with the wheels of a vehicle.

This arrangement permits driving the vehicle to a working area, and then shifting the apparatus to operate as a single or double pump, to perform operations required at the working area.

The apparatus of FIG. 7 cannot be reversed, that means that the direction of rotation of output shaft 911 cannot be reversed without also reversing the prime mover motor. This is possible in the embodiment of FIG. 9 which requires that the outlets and inlets of the two hydraulic units 3 and t are separate, as described with reference to the embodiments of FIGS. 2 and 3.

Referring now to FIG. 9, a channel 99 is connected with a conduit H2, and a channel 97 is connected with a conduit llll3. Conduits M2 and H3 are connected with a control valve 1 11d which has three inlets and three control positions. Control valve lid is preferably operated by electromagnetic means, only schematically indicated.

Channels 89 and 99 are connected by conduit I15 Control valve lid is connected by conduit llllti to a consumer. Two conduits Ill? and llllli connect the conduit 11115 with the second control valve 192. Conduit llll7' is connected by control valve 1992 with the auxiliary pump I94, and conduit lllti is connected through control valve I92 with a container 1193. in the control position ll of control valve T92, the auxiliary pump T99 is connected with the return conduit lll9 discharging into container I93.

The control valve llllll has another conduit I29 connected with conduit llll'i. A check valve I211 is provided in conduit M7, and a check valve i122 is provided in conduit 129. The check valves permit flow in the direction from control valve I92 to the hydraulic apparatus 3, i.

The hydraulic apparatus shown in FIG. 9 operates as a single pump when the control valve lll l is in control position III, the control valve I92. is in the control position ll, when the coupling '73 is disengaged, and when the coupling 93 does not connect shaft '79 with the output shaft 9Ill. The swash plate 9 is in the position shown in chain lines.

The pressure fluid pumped and displaced by the hydraulic unit 3 operating as a pump flows through conduit M2 to the valve lid and from the same through conduit lilo to a consumer. No pressure fluid can flow into the hydraulic unit l,

since the connection is interrupted by the control valve 14. Hydraulic unit 4 and shaft 70 are at a standstill, even if the swash plate 17 is in a position slanted to shaft 70. Pressure fluid is pumped from container 103 through conduits 1 18 and 115 to channel 88. The auxiliary pump 104 pumps fluid from container 103 through control valve 102 in position II back through discharge conduit 119 into container 103, or is not driven at all.

When the hydraulic unit 3 is to be used as a single motor, all that is necessary is to reverse the flow of the pressure fluid, which means that the high pressure fluid flows from conduit 116 through valve 114 and conduit 112 to the hydraulic unit 3.

When the hydraulic apparatus is to be used as a double pump, shafts 68 and 70 of the two units are connected by coupling 73, and the control valve 1 14 is placed in the control position II. In this position of the valve, pressure fluid is also pumped by hydraulic unit 4 acting as a pump through conduit 113 to control valve 114 where the fluid combines with the pressure fluid from the hydraulic unit 3. Both streams of pressure fluid flow through conduit 116 to the consumer. Fluid is sucked through conduits 118 and 1 from the container 103.

When the apparatus is to be used as a double motor, it is only necessary to reverse the direction of flow. The high-pressure side and low-pressure side remain the same irrespective of whether the apparatus is operated as a single pump or motor or as a double pump or motor.

When the hydraulic apparatus 3, 4 is to operate as a hydrostatic transmission, control valve 114 and control valve 102 are placed in the control positions I, as shown. Coupling 73 is disengaged, coupling 91 is engaged, so that only shaft 70 is connected with output shaft 91, while shaft 68 is connected to a prime mover. The swashplate 9 is in the same position as before, shown in chain lines.

The pressure fluid displaced by the hydraulic unit 3 operating as a pump flows through conduit 112 to the control valve 114 and from the same through conduit 1 13 and channel 87 to the hydraulic unit 4 so that the same is rotated. The high pressure side is at the channels 85 and 87. The system operates in a closed circuit, which means that the fluid discharged from the hydraulic unit 4 flows from channel 89 through conduit 115 directly to the channel 88 of the hydraulic unit 3 so that highpressure fluid flows in conduits 112 and 113.

As noted before, it is necessary to replace leakage losses when the apparatus operates as a hydrostatic transmission with a closed circuit. For this purpose, the auxiliary pump 104 pumps pressure fluid through control valve 102 into the conduit 117, and through the check valve 121 into conduit 115. The check valve 122 is closed since high pressure prevails in conduit 113. This check valve is required so that the fluid flowing at high pressure in conduits 112 and 113, cannot enter the low-pressure conduits 115 or 117. When shaft 68 is driven by the prime mover, not shown, in clockwise direction, output shaft 91 also rotates in clockwise direction.

If it is desired that the output shaft 91 rotates in counterclockwise direction, while the clockwise direction of rotation of shaft 68 is maintained, the hydrostatic transmission must be reversed.

For this purpose, the swashplate 9 is angularly tilted to opposite position, as shown in solid lines in FIG. 8. The hydraulic unit 3 now displaces pressure fluid through channel 88 and conduit 115 to channel 89 of the hydraulic unit 4 which is rotated in the opposite direction than before. The pressure fluid displaced by hydraulic unit 4 flows through conduit 113, control valve 114, and conduit 112 without pressure into the hydraulic unit 3. The pressure of the fluid in conduits 1 12 and 113 is now low. Control valves 102 and 114 remain in the same position when the direction of rotation of output shaft 91 is reversed as explained above.

The auxiliary pump 104 pumps through conduit 117 and check valve 122, pressure fluid into conduit 120 from where the fluid flows into the conduits l 12 and 113. The check valve 121 closes so that the high-pressure fluid in conduit 115 cannot flow into the low pressure conduit 120. The check valve 41 described with reference to FIG. 1 can be omitted, when the swashplate 17, as in conventional constructions, can also be tilted. In this event, the swashplate 17 must be placed in a neutral position perpendicularly to the axis of the respective shaft so that the hydraulic unit 4 cannot be rotated when the hydraulic unit 3 operates as a single pump or motor.

In the embodiment of FIG. 8, this danger is not present, even if the swashplate 17 is tilted, since all control functions are carried out by the control valve 114 so that under no circumstances, can pressure fluid from channel flow into channel 87 when hydraulic unit 3 operates as a single pump or single motor.

It is customary to drive the auxiliary pump 104 from one of the hydraulic units. When the apparatus is operated as pump or as motor, the auxiliary pump 104 circulates the fluid idly out of and into container 103. It is also possible to stop the auxiliary pump instead of permitting the idle operation. When the hydraulic apparatus is operated as a hydrostatic transmission 3, 4, the auxiliary pump pumps at a pressure of 4 to 8 atmospheres and discharges fluid into the low pressure side of the apparatus.

The valves 100, 102 and 114, and the couplings 19, 54, 73, 93 are advantageously operated by electromagnetic means, or hydraulically operated by remote control.

FIG. 1 shows in chain line a pulley directly mounted on shaft 18. Evidently, pulley 1 10 can be used as an output means connected to a driven apparatus when the embodiment of FIG. 1 is operated as a hydrostatic transmission. In other words, it is not necessary to provide an output shaft 91 and a corresponding coupling 93, as described with reference to FIGS. 3, 7 and 8. Whether coupling 93 and an output shaft 9! is provided, depends only on the available space. The conduits illustrated in FIGS. 7 and 8 outside of the housing in a schematic manner, can also be ducts or channels within valve bodies enveloped by the housing of the apparatus.

The hydraulic apparatus of the invention is particularly suited for an arrangement in which very different amounts of pressure fluid are required, or are available. The apparatus is particularly suited for vehicles, where the hydrostatic transmission can be used as a drive for the wheels, but is operated as a pump at the working area.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of hydraulic apparatus comprising two hydraulic units operable as motor or pump differing from the types described above.

While the invention has been illustrated and described as embodied in a hydraulic apparatus with two axially aligned hydraulic units in combination with control valve means which permit operation of the apparatus as pump, motor, or hydrostatic transmission, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

I claim:

1. Hydraulic apparatus with axially aligned hydraulic units, comprising, in combination, first and second hydraulic units having first and second stator means and first and second rotary means, respectively, said first and second rotary means having a common axis; connecting means having an engaged condition connecting said first and second rotary means for rotation about said common axis so that said first and second hydraulic units are simultaneously operated as pumps when said first rotary means is driven, and as hydraulic motors when a fluid medium under pressure is supplied to said first hydraulic units, and a disengaged condition disconnecting said first and second rotary means so that only said first hydraulic unit operates as pump or motor, respectively; and operating means for placing said connecting means selectively in said engaged and disengaged conditions.

2. Hydraulic apparatus as claimed in claim ll comprising a housing enveloping said first and second hydraulic units and said connecting means; and wherein said operating means are partly located outside of said housing.

3. Hydraulic apparatus as claimed in claim ll wherein said first and second rotary means have axially aligned first and second shafts having adjacent inner end portions; and wherein said connecting means include coupling means connecting and disconnecting said shaft end portions in said engaged and disengaged conditions, respectively.

4. Hydraulic apparatus as claimed in claim 3 wherein said coupling means include outer peripheral axially extending coupling projections and recesses on said shaft end portions, and a coupling sleeve having inner axially extending coupling recesses and projections engaging said coupling recesses and projection of one of said shaft end portions, and engaging also said coupling recesses and projections of the other shaft end portion in said engaged condition for connecting said first and second shafts for rotation while axially aligning said shaft end portions; and comprising first and second bearing means for supporting said first and second shafts spaced from said end portions so that said coupling sleeve functions as a bearing.

5. Hydraulic apparatus as claimed in claim 4 wherein said operating means are connected with said coupling sleeve for moving the same in axial direction between engaged and disengaged positions, respectively, for connecting and disconnecting said shaft end portions.

6. Hydraulic apparatus as claimed in claim 3 wherein said coupling means include a coupling sleeve mounted on one of said shaft end portions for axial movement and being connected with the same for rotation in said disengaged condition, and enveloping both said shaft end portions in said engaged condition, and being connected also with the other shaft end portion for rotation in said engaged condition; and wherein said coupling sleeve has a bearing portion supporting the other shaft end portion for rotation so that said shaft end portions are aligned with each other whereby said coupling sleeve performs the function ofa bearing.

7. Hydraulic apparatus as claimed in claim 1 wherein said first and second hydraulic units are first and second axial piston pumps; wherein said first and second rotary means include axially aligned first and second shafts, tiltable swash plates on said first and second shafts, and first and second cylinder and piston means on said first and second shafts; wherein said first and second hydraulic units include valve plate means between said first and second cylinder and piston means, said valve plate means having inlets and outlets for said first and second hydraulic units; wherein said connecting means comprise coupling means for said first and second shafts; and comprising a housing enveloping said first and second hydraulic units and said coupling means.

8. Hydraulic apparatus as claimed in claim ll wherein said connecting means include coupling means for connecting and disconnecting said first and second rotary means; wherein said operating means include lever means connected with said coupling means for operating the same; and comprising a housing enveloping said first and second hydraulic units and said coupling means, and having a sealed opening through which said lever means projects for manual operation of said coupling means.

9. Hydraulic apparatus as claimed in claim d wherein at least one of said rotary means includes a shaft; wherein said coupling means is mounted on the other rotary means for axial ill movement between engaged and disengaged positions; and

wherein said operating means include an annular operating means connected w1th said shaft for rotatlon and mounted on said shaft for axial movement, means connecting said annular operating means with said coupling means, and means connecting said annular operating means with said lever means so that said coupling means can be operated by said lever means.

llti. Hydraulic apparatus as claimed in claim 1 wherein said first rotary means includes a first shaft adapted to be driven by a prime mover when said first hydraulic unit operates as a pump; wherein said second rotary means includes a second shaft axially aligned with said first shaft and adapted to serve as an output shaft when said second hydraulic unit is operated as a hydraulic motor; and comprising valve means having a control position for hydraulically connecting said first and second hydraulic units when said connecting means is in said disengaged condition so that said first hydraulic unit operating as a pump drives said second hydraulic unit operating as a hydraulic motor whereby said first and second hydraulic units form a hydrostatic transmission, said. valve means having another position for guiding fluid from at least one of said hydraulic units to a consumer outlet.

llll. Hydraulic apparatus as claimed in claim 10 comprising an output shaft means; and a coupling for connecting said second shaft with said output means when said first shaft is driven by the prime mover and said first and second hydraulic unit operate as a hydrostatic transmission.

12. Hydraulic apparatus as claimed in claim ll wherein said first rotary means includes a first shaft adapted to be driven by a prime mover so that said first rotary unit operates as a pump; wherein said second rotary means includes a second shaft adapted to serve as an output shaft when said connecting means is in said disengaged condition and said second hydraulic unit operates as a hydraulic motor, and adapted to serve as a drive shaft for said second hydraulic unit operating as a pump when said connecting means is in said engaged condition; comprising valve means and conduit means hydraulically connecting said first and second hydraulic units, said valve means being operable between a first control position in which in said disengaged condition of said connecting means only said first hydraulic unit operates as a pump, a second control position in which in said engaged condition of said connecting means said first and second hydraulic units both operate as pumps, and a third control position hydraulically connecting said first and second units so that in said disengaged condition of said connecting means, said second hydraulic unit operates as a hydraulic motor hydraulically driven by said first unit operating as a pump and forming a hydrostatic transmission with the same.

13. Hydraulic apparatus as claimed in claim 12 comprising an auxiliary pump and a container for a fluid medium communicating with the low-pressure inlet of said auxiliary pump; and wherein said third control position said valve means hydraulically connect the high'pressure outlet of said auxiliary pump with the input of said first hydraulic unit operating as a pump.

id. Hydraulic apparatus as claimed in claim 13 wherein said valve means include a first valve having a first position hydraulically connecting in said first control position the output of said first hydraulic unit with a consumer, a second position connecting in said second control position the outlets of both said first and second hydraulic units with the consumer, and a third position connecting in said third control position the outlet of said first hydraulic unit with the input of said second hydraulic unit, and a second valve having a first position con necting in said third control position the output of said auxiliary pump with the output of said second hydraulic unit and with the input of said first hydraulic unit, and a second position connecting in said first and second control positions the inlet of said first hydraulic unit and the outlet of said auxiliary pump with said container. 

1. Hydraulic apparatus with axially aligned hydraulic units, comprising, in combination, first and second hydraulic units having first and second stator means and first and second rotary means, respectively, said first and second rotary means having a common axis; connecting means having an engaged condition connecting said first and second rotary means for rotation about said common axis so that said first and second hydraulic units are simultaneously operated as pumps when said first rotary means is driven, and as hydraulic motors when a fluid medium under pressure is supplied to said first hydraulic units, and a disengaged condition disconnecting said first and second rotary means so that only said first hydraulic unit operates as pump or motor, respectively; and operating means for placing said connecting means selectively in said engaged and disengaged conditions.
 2. Hydraulic apparatus as claimed in claim 1 comprising a housing enveloping said first and second hydraulic units and said connecting means; and wherein said operating means are partly located outside of said housing.
 3. Hydraulic apparatus as claimed in claim 1 wherein said first and second rotary means have axially aligned first and second shafts having adjacent inner end portions; and wherein said connecting means include coupling means connecting and disconnecting said shaft end portions in said engaged and disengaged conditions, respectively.
 4. Hydraulic apparatus as claimed in claim 3 wherein said coupling means include outer peripheral axially extending coupling projections and recesses on said shaft end portions, and a coupling sleeve having inner axially extending coupLing recesses and projections engaging said coupling recesses and projection of one of said shaft end portions, and engaging also said coupling recesses and projections of the other shaft end portion in said engaged condition for connecting said first and second shafts for rotation while axially aligning said shaft end portions; and comprising first and second bearing means for supporting said first and second shafts spaced from said end portions so that said coupling sleeve functions as a bearing.
 5. Hydraulic apparatus as claimed in claim 4 wherein said operating means are connected with said coupling sleeve for moving the same in axial direction between engaged and disengaged positions, respectively, for connecting and disconnecting said shaft end portions.
 6. Hydraulic apparatus as claimed in claim 3 wherein said coupling means include a coupling sleeve mounted on one of said shaft end portions for axial movement and being connected with the same for rotation in said disengaged condition, and enveloping both said shaft end portions in said engaged condition, and being connected also with the other shaft end portion for rotation in said engaged condition; and wherein said coupling sleeve has a bearing portion supporting the other shaft end portion for rotation so that said shaft end portions are aligned with each other whereby said coupling sleeve performs the function of a bearing.
 7. Hydraulic apparatus as claimed in claim 1 wherein said first and second hydraulic units are first and second axial piston pumps; wherein said first and second rotary means include axially aligned first and second shafts, tiltable swash plates on said first and second shafts, and first and second cylinder and piston means on said first and second shafts; wherein said first and second hydraulic units include valve plate means between said first and second cylinder and piston means, said valve plate means having inlets and outlets for said first and second hydraulic units; wherein said connecting means comprise coupling means for said first and second shafts; and comprising a housing enveloping said first and second hydraulic units and said coupling means.
 8. Hydraulic apparatus as claimed in claim 1 wherein said connecting means include coupling means for connecting and disconnecting said first and second rotary means; wherein said operating means include lever means connected with said coupling means for operating the same; and comprising a housing enveloping said first and second hydraulic units and said coupling means, and having a sealed opening through which said lever means projects for manual operation of said coupling means.
 9. Hydraulic apparatus as claimed in claim 8 wherein at least one of said rotary means includes a shaft; wherein said coupling means is mounted on the other rotary means for axial movement between engaged and disengaged positions; and wherein said operating means include an annular operating means connected with said shaft for rotation and mounted on said shaft for axial movement, means connecting said annular operating means with said coupling means, and means connecting said annular operating means with said lever means so that said coupling means can be operated by said lever means.
 10. Hydraulic apparatus as claimed in claim 1 wherein said first rotary means includes a first shaft adapted to be driven by a prime mover when said first hydraulic unit operates as a pump; wherein said second rotary means includes a second shaft axially aligned with said first shaft and adapted to serve as an output shaft when said second hydraulic unit is operated as a hydraulic motor; and comprising valve means having a control position for hydraulically connecting said first and second hydraulic units when said connecting means is in said disengaged condition so that said first hydraulic unit operating as a pump drives said second hydraulic unit operating as a hydraulic motor whereby said first and second hydraulic units form a hydrostatic Transmission, said valve means having another position for guiding fluid from at least one of said hydraulic units to a consumer outlet.
 11. Hydraulic apparatus as claimed in claim 10 comprising an output shaft means; and a coupling for connecting said second shaft with said output means when said first shaft is driven by the prime mover and said first and second hydraulic unit operate as a hydrostatic transmission.
 12. Hydraulic apparatus as claimed in claim 1 wherein said first rotary means includes a first shaft adapted to be driven by a prime mover so that said first rotary unit operates as a pump; wherein said second rotary means includes a second shaft adapted to serve as an output shaft when said connecting means is in said disengaged condition and said second hydraulic unit operates as a hydraulic motor, and adapted to serve as a drive shaft for said second hydraulic unit operating as a pump when said connecting means is in said engaged condition; comprising valve means and conduit means hydraulically connecting said first and second hydraulic units, said valve means being operable between a first control position in which in said disengaged condition of said connecting means only said first hydraulic unit operates as a pump, a second control position in which in said engaged condition of said connecting means said first and second hydraulic units both operate as pumps, and a third control position hydraulically connecting said first and second units so that in said disengaged condition of said connecting means, said second hydraulic unit operates as a hydraulic motor hydraulically driven by said first unit operating as a pump and forming a hydrostatic transmission with the same.
 13. Hydraulic apparatus as claimed in claim 12 comprising an auxiliary pump and a container for a fluid medium communicating with the low-pressure inlet of said auxiliary pump; and wherein said third control position said valve means hydraulically connect the high-pressure outlet of said auxiliary pump with the input of said first hydraulic unit operating as a pump.
 14. Hydraulic apparatus as claimed in claim 13 wherein said valve means include a first valve having a first position hydraulically connecting in said first control position the output of said first hydraulic unit with a consumer, a second position connecting in said second control position the outlets of both said first and second hydraulic units with the consumer, and a third position connecting in said third control position the outlet of said first hydraulic unit with the input of said second hydraulic unit, and a second valve having a first position connecting in said third control position the output of said auxiliary pump with the output of said second hydraulic unit and with the input of said first hydraulic unit, and a second position connecting in said first and second control positions the inlet of said first hydraulic unit and the outlet of said auxiliary pump with said container. 